Intravenous therapy employing catheter assemblies frequently requires that the patency, or open condition of the catheter, be maintained during periods between infusion of nutritional or therapeutic solutions. In the past, several different approaches have been taken for achieving patency maintenance, with varying degrees of effectiveness.
One approach, usually referred to as KVO, or "keep vein open", entails substantially continuously infusing a non-therapeutic solution, such as saline, into the patient. Flow rates on the order of 5-125 milliliters per hour are typical, and can be effected by either gravity-flow or infusion pump systems. While this type of therapy is generally regarded as effective for patency maintenance, it will be appreciated that the essentially uninterrupted nature of the therapy results in relatively high cost, as well as the infusion of liquid which might otherwise not be required by the patient.
Alternate approaches entail formation of solution "locks" by essentially flooding the catheter with a non-therapeutic solution between infusions. The use of heparin, an anti-coagulant, as a fluid lock is generally regarded as effective for patency maintenance, with the added advantages, compared to KVO therapy, of patient mobility, minimal nursing attention, and minimal fluid introduction to the patient. On balance, the use of a heparin lock has the disadvantages of the attendant "SASH" procedure (flush with saline, infusion with antibiotic, followed by saline flush, and reestablishment of the heparin lock), as well as the potential incompatibility of heparin with many antibiotic solutions.
Alternately, saline locks can be employed, with the saline substituted for the heparin solution in the catheter. However, the effectiveness of saline locks is generally regarded to be less than that of the aforementioned patency maintenance techniques.
Consistent and cost-effective patency maintenance is desirable for efficient intravenous therapy. The present invention contemplates a desirably straightforward patency maintenance arrangement which specifically addresses the drawbacks associated with currently used techniques.